As is known, a grinding/drilling machine comprises one or more machining heads; and a feed assembly for feeding the work sheet along a grinding path, or holding the sheet in a given reference position.
Known feed assemblies normally comprise one or more pairs of belt conveyors; each conveyor comprises a draw belt, which defines a supporting surface for the work sheet and has a row of recesses, each formed through the draw belt and having an opening that comes out on the supporting surface and is closed in use by the glass sheet; and each recess is bounded by a bottom wall, in which are formed one or more passages connecting the recess to a suction source.
In actual use, depending on the size of the sheets and/or the distance between consecutive sheets on the conveyor, at least one and normally more than one of the recesses often remain partly or even fully open. And, given the degree of contamination of the workplace by dust and/or glass grinding chips and/or coolant, it is only a matter of time before the recesses become clogged, thus gradually impairing the ability of the conveyor to retain the sheet. For this reason, known conveyors must be thoroughly cleaned every so often, which involves both direct labour and indirect downtime expense.
Moreover, despite the suction in each recess or group of recesses being controlled according to the location of the recesses, the fact that some of them are often fully open greatly increases suction air consumption, at considerable cost over time, and at any rate makes it necessary to employ high-performance suction systems.
Lastly, the presence, and especially the size of the openings in the recesses, result in local weakening of the draw belt.